Stromboli is one of the seven islands that make up the archipelago of the Aeolian Islands. It is considered one of the most active volcanoes in the world, in view of its persistent open duct eruptive activity, called precisely "Strombolian". Every 10-20 minutes, in fact, there are explosions of moderate energy, with the launch of shreds of incandescent lava, lapilli and ash up to a few hundred meters high. The explosions originate from several mouths, aligned in a north-east south-west direction, located inside a crater terrace at an altitude of about 700m in the upper part of the Sciara del Fuoco, one of the slopes of the volcano.
In addition to the so-called "ordinary" explosive activity, the craters are periodically affected by other types of explosions: the "major" ones and the "paroxysmal" ones. Major explosions can occur several times a year and can cause the relapse of heavy materials - rock blocks and volcanic bombs - in the upper part of the volcano, while the "paroxysmal" have a return time of a few years and can throw heavy materials at a greater distance, affecting even the lowest altitudes, and also reach the towns, as happened during the eruption of April 5, 2003. Sometimes, the explosive activity can give way to lava flows that flow along the Sciara del Fuoco.
Eruptive phenomena, in particular lava flows and paroxysmal explosions, can destabilize the slope of the Sciara del Fuoco causing landslides involving the emerged and/or submerged parts of the structure. The landslides can also trigger tidal waves with effects along the coasts of the island itself, as well as Panarea and possibly other Aeolian islands, Calabria and Sicily.
Explosions of greater energy can finally create conditions of risk both in the upper part of the mountain and, to a lesser extent, in the inhabited areas. On the island there are two inhabited centres: Stromboli and Ginostra, located respectively in the north-eastern and south-western sectors.
Currently the alert level for Stromboli is yellow.
The monitoring parameters are normal with a persistent volcanic activity of the Strombolian type and of ordinary intensity.
Every month, the Civil Protection Department organizes videoconferences with the Centers of Competence responsible for monitoring volcanic activity on Stromboli: the National Institute of Geophysics and Volcanology (Ingv) of Catania, Naples and Palermo and the Department of Earth Sciences, University of Florence. The Department of Civil Protection of the Sicilian Region also participates in the videoconferences.
According to the phenomena and risk assessments made available by the Centers of Competence, the Department of Civil Protection declares the levels of alert and operational phases in close collaboration with the structure of civil protection of the Sicilian Region, after hearing the opinion, if the timing and mode of evolution of volcanic phenomena allow it, the Commission Great Risks - Volcanic Risk Sector.
At the end of the videoconferences, the Department issues a document in which the results of the videoconferences are reported.
Currently the level of alert for the Stromboli is yellow.
The Department of Civil Protection, in agreement with the Sicilian Region and with the support of the Centers of Competence, as of 1 December 2015 implemented several modifications to the structure of the national warning system for volcanic risk. In particular, for the Stromboli volcano, these changes were designed to better frame the responsibility profiles and competences of the different institutional and territorial levels, with respect to risk assessment and to the activation of the operational response in case of local or national impact scenarios.
Alert levels. Alert levels describe the state of volcano activity, i.e. whether the volcano is in a stable or unstable condition. A combination of monitoring parameters and data from any ongoing events are used to identify them. They are represented by four colors - green, yellow, orange and red - which are indicative of the possible evolution of the state of volcano activity towards event scenarios "of national importance", which require to be faced with extraordinary means and powers, through the coordinated intervention of a plurality of subjects (art.2, paragraph 1 letter c of Law 225/92).
Declaration of alert levels. The levels of alert are declared by the Department of Civil Protection, in close collaboration with the structure of civil protection of the Sicilian Region, after hearing the opinion, if the timing and mode of evolution of volcanic phenomena allow, the Commission Great Risks - Volcanic Risk Sector.
The assessment is based on the reports of the phenomena and hazard assessments made available by the Centers of Competence that for the Stromboli are the Etna Observatory of the National Institute of Geophysics and Volcanology and the University of Florence. The Civil Protection Department shares all this information with the civil protection structure of the Sicilian region that, especially in relation to scenarios of local impact, has the task of alerting the territorial structures of civil protection and adopt any measures in response to emergency situations.
Passage of alert level. The passage from one level of alert to the other can occur before the event, if the information provided by the Centers of Competence allow it. Otherwise, the transition can be decreed when the phenomenon is observed, therefore, occurred or in progress. It is worth highlighting that the passage of the alert level may not necessarily occur sequentially or gradually, since sudden or abrupt changes in volcanic activity are always possible, even completely unexpected.
It is worth to note that some phenomena of the Stromboli are completely unpredictable and sudden, so even when the alert level is "green" there is always a risk. When these events occur, the alert level is not automatically modified, because a " local emergency" situation occurs, which calls for the activation of the operational response of the territorial structures of civil protection.
In August 2015, the latest version of the National Emergency Planning for Stromboli Island was approved. The document sets out the main activities that must be implemented in the Island of Stromboli following a tsunami triggered by a landslide of significant portions of the slope of the Sciara del Fuoco, requiring the activation of the national level of civil protection.
National Emergency Plan
The reference scenario of the plan is related to the landslide and the consequent tsunami occurred on December 30, 2002. Specific planning has not been elaborated for further scenarios of national relevance, that are possible but rare and with a temporal scale of recurrence from pluricentennial to millennial, such as the total collapse of the Sciara del Fuoco slope or the opening of eruptive mouths outside the Sciara del Fuoco, with the formation of flows that could affect populated areas. Indeed, for the latter two types of events, and in any case for tsunamis triggered by sudden phenomena or with limited forewarning, including seismically induced landslides, the operational measures provided for in the operational phases described in the Plan can be adopted with particular regard to the actions of safety and relief to the population.
The Plan consists of a first part that provides information on geography, volcanology, monitoring of Stromboli and support for operational management; a second part dedicated to the alert levels and the reference scenario for planning and a third part in which are described the three different operational phases (Warning, Pre-alarm and Alarm), the actions and activities that the competent parties involved are required to implement in order to achieve the objectives of operational management. The document is supplemented by four annexes dedicated to maritime and air accessibility, the map showing the tsunami wave of December 30, 2002 and the outline of the technical and scientific assessment activities.
History of the plan
The national emergency planning activities for the Island of Stromboli have followed an articulated path, started in 2003, which saw the participation and involvement of the Sicilian Region, the Prefecture - UTG of Messina and the Municipality of Lipari and ended with the approval, in August 2015, of the "National Emergency Plan for volcanic events of national importance".
The first national planning document was elaborated during the emergency events that affected the island from the end of 2002 to 2003. In that period in fact, an effusive phase of the volcano started on 28 December 2002 and followed two days later, on 30 December 2002, by a landslide along the Sciara del Fuoco and a consequent seaquake, determined the predisposition of a first planning of civil protection for the management of the emergency deriving from the risk of seaquake for the Island of Stromboli and for the other islands of the archipelago of the Aeolian Islands.
Subsequently, following a new volcanic crisis started in the early months of 2007, the procedures have been formulated in relation to the modalities of alerting and activation of the operational structures of the civil protection system present on the territory, with the aim of being able to promptly dispose of suitable means for the first assistance of the population, as well as the subsequent possible evacuation of the population present on the island of Stromboli.
In 2010 the former planning was updated and integrated through the drafting of a new document, on the basis of increased scientific knowledge, the experience gained during the emergency phases, but also following a moment of verification of procedures carried out on the island on April 19, 2005, through a national exercise of civil protection. Due to an increase in the eruptive activity of the volcano occurred from May to August 2014, new procedures have been defined for the removal, partial or total, of the population from the Island of Stromboli.
Ordinary activity. The explosions of the volcano are characterized by ordinary explosions of lava, gas and ash, even hundreds of meters high, associated with the fallout of heavy materials mostly within the crater terrace. The paths used for the ascent to Pizzo Sopra la Fossa, from which it is possible to observe the entire crater terrace, are not usually affected by the fallout of volcanic material.
Sometimes the explosive activity of the volcano is accompanied by lava emissions that pour in the form of flow inside the Sciara del Fuoco, a wide depression that originated more than 5,000 years ago from the collapse of the eastern side of the volcano.
The persistent activity of the volcano and the lava effusions do not represent a source of immediate danger for the towns and for the excursionists although the effusive activity can cause instability on the side of the Sciara del Fuoco, causing landslides and, consequently, tsunamis.
The phenomena that cause danger outside the Sciara del Fuoco are major explosions and tsunamis.
Major explosions. The major explosions can occur many time during the year and can cause the fall of heavy materials - rocky blocks and volcanic bombs - in the upper part of the volcano.
Paroxysmal Explosions. The paroxysmal explosions are sudden and consist in real " cannons ", accompanied by strong detonations, with launch of material and stones at some kilometers from the craters. The fall of heavy materials interests the high part of the mountain and occasionally the inhabited centers. The incandescent materials, falling along the slopes, can trigger vegetation fires. During the most violent explosive episodes (eruption of 1930) avalanches of hot material can occur and flow inside depressed areas of Vallozzo and Rina Grande/Schicciole up to the sea.
Tsunamis. They occur usually during violent explosions or large landslides. In the last 100 years five tsunamis occurred: in 1916, 1919, 1930, 1944 and 2002. The latter was triggered by a large underwater landslide that spread to the emerged part with an average intensity higher than the others. The surveillance system operating in Stromboli and centralized at the Advanced Operations Center can identify the potential occurrence of such phenomena and inform the population.
A multi-parameter monitoring system is in force on Stromboli, which constantly checks the significant parameters of the volcanic activity and the landslides of the Sciara del Fuoco.
The network is composed of different systems: seismic, acoustic, geochemical, soil deformation (Gps, clinometric), magnetic, gravimetric, visual with optical and thermal cameras. To monitor the slope of the Sciara del Fuoco and any landslide phenomena have been installed two synthetic aperture radar interferometers (SAR), while for the detection of any tsunami has been installed a buoy off the island. A second buoy, with identical characteristics to the first, will soon be installed to strengthen the system.
The structures responsible for monitoring volcanic activity in Stromboli are the Etnean Observatory - Catania Section of the National Institute of Geophysics and Volcanology (Ingv), the Ingv of Palermo and the Department of Earth Sciences, University of Florence.
The signals of all the monitoring stations are transmitted in real time to the Advanced Operations Centre of the Municipality of Lipari and to the operations rooms of the scientific bodies in charge of monitoring, where the signals are acquired, analyzed and processed, to improve the understanding of the general state of the volcanic system.
Alcuni fenomeni pericolosi, come le esplosioni parossistiche e i maremoti, possono avvenire repentinamente, a prescindere dal livello di allerta in corso. Per questo motivo, sull’isola sono attivi due sistemi sperimentali di Early Warning automatici che allertano la popolazione tramite sirene:
- un sistema per le esplosioni parossistiche, in grado di fornire l’allarme alcuni minuti prima dell’esplosione, che avvisa la popolazione con un suono di sirene a due tonalità alternate;
- un sistema per il maremoto, in grado di fornire l’allarme alcuni minuti prima dell’arrivo delle onde sulle coste dell’isola, che avvisa la popolazione con un suono di sirene a una sola tonalità.
Impara a riconoscere i suoni delle sirene e le norme di comportamento da adottare in caso di evento.
Stromboli, the northernmost island of the Aeolian Islands, has the morphology of a regular cone with steep slopes that rise from a depth of 1500-2000m below sea level. The active craters are located at 700m a. s. l., in the upper part of the Sciara del Fuoco, a depression that was formed about 5000 years ago by the collapse of the north-eastern side of the volcanic building.
The island was built up over the course of several volcanic eruptions. Initially the activity took place where today there is the rock of Strombolicchio, a residual of an active volcanic pipe about 200,000 years ago. Later, the activity moved about 3 km to the south-west, leading to the gradual building of the current strato-volcano.
The eruptive history of Stromboli can be divided into cycles divided by major structural events, like calderic and flank volcanic collapses.
During the last 13,000 years, the cone has undergone significant changes: the eruptive activity has led first to the construction of the summit, the Vancori peak, and then produced important accumulations of lava on the northwestern slopes, also by lateral eruptive mouths, such as the Timpone del Fuoco. At least three major landslides on the northeastern slope occurred during the same period, giving rise to the Sciara del Fuoco.